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Home , Ammonium nitrate

3,366,053 United States Patent Office Patented Jan. 30, 1968

2 3,366,053 that can be dissolved by a given amount of water. AMMONUM NITRATE MIXTURE Subsequently either excess water was dried out or the George L. Griffith, Coopersburg, George A. Lyte, Bethle mass was cooled and this causes part of the hem, and Fraiklin B. Wells, Emmaus, Pa., assignors to nitrate to go out of solution with the formation of new Trojan Powder Company, a corporation of New York crystals. It is a recognized fact that such newly formed No Drawing. Filed Oct. 29, 1958, Ser. No. 770,302 crystals cement together the original crystals of the mix 3 Clains. (C. 102-24) ture and form the mass into a compacted solidified whole. This is illustrated for example in Woodbury et al. Patent This invention relates to an ammonium nitrate-based No. 2,603,572. explosive mixture which includes not over about 4% IO The water must be free water. Water in hydrated or aluminum in finely-divided form and which is sensitized other bound form is ineffective. Apparently, the increase by a small amount of water. in sensitivity is due to some action of free water on one Ammonium nitrate-based constitute an im or more of the components present and not to some portant proportion of the sales volume of explosive mix effect during the detonation, under which conditions the tures. Ammonium nitrate explosives are generally charac 5 hydrated water ought to be liberated and then made terized by a low sensitiviey to detonation, and hence it available as free water. is customary to combine with the ammonium nitrate an This increased sensitivity is obtained with mixtures ingredient which sensitizes the explosive. For this purpose containing additional explosive components both of the materials can be used which are themselves detonatable, detonating and nondetonating type. Of the detonating but many desirable materials which are employed are not 20 components which can be used nitrostarch is preferred. themselves detonatable, and nonetheless sensitize the Also useful are nitroglycerin, a mixture of 60% cyclo ammonium nitrate. trimethylenetrinitramine, 40% trinitrotoluene and from The ability of a substance to act as a sensitizer is in 1 to 4% paraffin wax, trinitrotoluene and other nitro no way related to its own sensitivity to detonation, but toluenes, nitronaphthalenes, pentaerythritol tetranitrate, is based upon unknown and unpredictable factors. A sur 25 a mixture of 1:1 pentaerythritol tetranitrite and trinitro prising variety of materials are effective sensitizers. toluene and cyclotrimethylenetrinitramine. These would Detonatable sensitizers include nitroglycerin and nitro usually be used in amounts ranging from 0 to about 12%, starch, and among the effective nondetonatable sensitizers preferably from 7 to 12%. are inorganic materials, such as particulate metals and The mixture of 60% cyclotrimethylenetrinitramine, particularly flake and powdered aluminum. 30 40% trinitrotoluene and from 1 to 4% paraffin wax is Certain substances have a desensitizing effect on commonly called in the trade “composition B," and for ammonium nitrate-based explosives. For example, water the purpose of simplicity we use such name as indicating has been known to be a desensitizer. It also causes setting, that composition. In the same way, the mixture of 1:1 and usually has been considered undesirable. pentaerythritol tetranitrite and trinitrotoluene is com in accordance with the instant invention, it has been 35 monly known in the trade as "pentolite' and again we determined that an amout of water within the range use the term “pentolite' as defining such material. Like from 1 to 6% and preferably from 1.25 to 5% will wise the cyclotrimethylenetrinitramine is commonly considerably increase the sensitivity to detonation of ex known as “cyclonite” and again we use that term as plosive mixtures based on ammonium nitrate as the defining the materials specified. principal explosive component and containing not over 40 There can also be included materials consisting largely 4% aluminum. This increased sensitivity is evidenced in of carbon such as coal, charcoal, carbon black, lamp detonation by a much less powerful blasting cap. The black, bagasse, nut and wood flours and meals and starch. fact that sensitivity is increased by water in this instance These would be used in an amount within the range from is particularly surprising, in view of the previous ex 0 to about 7%, preferably from 5 to 7%. perience in the art that water is a desensitizer for such 45 Rosin and metallic resinates, hexamethylene tetramine explosives. and paraffin oils and waxes such as mineral oil also can Undoubtedly, the increased sensitivity is closely be included in small amounts, usually not in excess of correlated with the proportions of the three essential 0.4%. ingredients, the ammonium nitrate, aluminum and water, Stabilizers such as , magnesium oxide which have been found to be critical in obtaining the 50 and like inorganic salts, which are well known to those result. Less than 1% water has been found to have little skilled in the art, can also be incorporated. Such materials or no sensitizing action. An increase in the amount of would usually be used in an amount up to about 0.5%. water beyond 6% with the aluminum not over 4% as The invention is applicable not only to ammonium ni stated also results in loss of the sensitizing effect. How trate but also to mixtures thereof with alkali metal ever, the use of water in the small amounts called for 55 by the invention which is simply admixed with the other such as and . In such mix ingredients under normal atmospheric conditions as here tures the ammonium nitrate would be present in major in described does not cause setting of the mixture in any proportion, of the order of 75% to 95%, and the alkali way, nor is the mixture hardened to an appreciable extent. metal nitrate in the proportion from 5 to 25%. Cartridges of the mixture may easily be penetrated by the The particle size of the nitrate can be adjusted to meet priming awl. 60 the need. Ordinary commercial mill ammonium nitrate is It may be noted that in the past water has under perfectly satisfactory. In some cases, coarse nitrate having special circumstances been added to explosives containing a grain size passing a standard No. 6 sieve and held on a ammonium nitrate but in such case the water was used standard No. 10 sieve is desirable. to cause the ammonium nitrate to go into solution either 65 The mixture is readily prepared by dry mixing the in by having a large amount of water present or by heating gredients. The water is itself absorbed in or on the solid the mixture which increases the amount of ammonium particles of the mixture during mixing. 3,366,053 3 4. The following examples in the opinion of the inventors Example 4 represent the best embodiments of their invention. This example shows that the water which is present must Example I be free water. Hydrated water or bound water is not effective. Commercial mill ammonium nitrate (98 parts) was 5 intimately mixed with 2 parts of powdered aluminum and tested by loading in to 1" x 4' cartridges to a density of 0.98 and detonating. The mixture was completely deto nated with a standard No. 8 blasting cap, but not with a E F G No. 6 blasting cap. O Ammonium Nitrate-Sodium Ni A second mixture was prepared using the same propor trate 5:l------53. 44 5.04 51.04 Ammonium Nitrate passing a tions with the addition of 1% water to the mixture. The Standard No. 10 sieve 26.15 25.00 25.00 material detonated with a No. 2 blasting cap, showing AluminuIn Powder------1.57 i. 50 50 Nitrostarch------2.09 11. 55 11.55 that it had been sensitized to a remarkable degree by sim Calcium Carbonate- - - - 0.20 0.20 - 0.20 ple addition of the water. A similar mixture containing 5 Wood Flour------6, 54 6.25 6.25 97 parts mill ammonium nitrate, 2 parts aluminum, 1 part Carbon Black------0.01 0, 0. 0.01 oil and 1 part water also detonated with a No. 2 cap. Water------4.451------A third mixture was prepared containing 96 parts of Boraxhydrate).------(Sodium tetraborate deca 9.6 commercial mill ammonium nitrate and 4 parts of pow 00, 00 100.00 205.5 dered aluminum. This material was loaded to a density of 20 Loading Density------1.08-1.0 1. 48-i. 52 1, 16 1.00, and found to be sensitive to a No. 6 cap. A fourth mixture made exactly as the third but containing 1.25% 1 4.5% Bound H.O. water was sensitive to a No. 1% blasting cap. 2 Parts. A fifth mixture prepared from 98.5 parts commercial mill ammonium nitrate and 1.5 parts powdered aluminum 25 and loaded to a density of 0.99 was found to be sensitive The water-containing mixture was sensitive to a No. 8 to a No. 14 cap. The same mixture containing 1 part water blasting cap, whereas the dry mixture required a No. 10 was sensitive to a No. 4 cap. blasting cap. Again, the water considerably increased the In all cases, the increase in sensitivity due to the water sensitivity. was outstanding. The Mixture G, containing water in bound form as the Example 2 30 hydrate of sodium tetraborate, was slightly more dense than Mixture E, but this difference was not sufficiently Two formulations were prepared based on ammonium great to cause any problem in use. However, this material nitrate and nitrostarch as the detonating sensitizer. These was even less sensitive than the dry mixture and required mixtures were practically identical, save for the presence a No. 16 blasting cap. This mixture contained bound water of water, and were as follows: 35 equivalent to 4.45% water if available, and this shows therefore that the water must be free before detonation can be affected. Bound water is useless, even though this A. B Water would be expected to be liberated at an elevated 40 temperature. Mill Ammonium Nitrate. 82.72 8.89 Example 5 Aluminum Powder------1.77 .75 Nitrostarch------9.9 9. 10 Calcium Carbonate------0.10 0.0 Powdered Anthracite Coal 6.21 6.5 The formulations E and F of Example 4 were prepared Carbon Black------0.01 0.0. in the same way, except that ground Pentolite was sub Water------1.00 45 stituted for nitrostarch. The dry mixtures were sensitive 100.00 00.00 to a No. 10 blasting cap, whereas the wet mixtures were Loading Density------0,98-1.00 .00-102 sensitive to a No. 8 blasting cap. - The densities of the mixtures with and without water were comparable to those of Example 4E and F. The mixture containing water was negligibly denser 50 Example 6 than the mixture which did not. It was sensitive to a No. 1 blasting cap, whereas the dry mixture required a No. The formulations E and F of Example 4 were prepared 2% cap. Thus, this small amount of water greatly in in the same way, except that Composition B was sub creased sensitivity. stituted for nitrostarch. The dry mixtures were sensitive Example 3 55 to a No. 10 blasting cap, whereas the wet mixtures were This example illustrates the use of mixed nitrates, and sensitive to a No. 8. a somewhat higher proportion of water: Example 7 The formulations of E and F of Example 4 were pre C D 60 pared in the same way except that the nitrostarch was replaced by the same weight of dry trinitrotoluene. The Ammonium Nitrate-Sodium Nitrate 5:1 - 82.59 80.69 Aluminum Powder------2.05 2.00 dry TNT mixture was sensitive to a No. 10 blasting cap, Nitrostarch.------7.88 7.70 whereas the moist mixture gave almost complete detona Magnesium. Oxide-- - - 0.10 0.10 Wood Flour------7.37 7.20 65 tion with a No. 8 blasting cap and was easily detonated Carbon Black------0.01 0.01 with a No. 10 cap. Water------2.30 Example 8 100.00 100, 00 Loading Density------1.055 1.19 The formulations of E and F of Example 4 were pre 70 pared in the same way except that the nitrostarch was The loading densities of these mixtures were not sig replaced by the same weight of Cyclonite (RDX). The nificantly different. The water-containing mixture was sen dry RDX mixture detonated fully with a No. 10 cap and sitive to a No. 8 blasting cap, whereas the dry mixture almost completely with a No. 8 cap. The RDX mixture required a No. 10 cap, showing the increase in sensitivity which was moistened with the 4.45% water was sensitive due to the Water. 75 to a No. 7 cap. 3,366,053 5 6 Example 9 ingredients. Proportions of optional components are by The following example illustrates the different effects weight of the entire mixture. obtained with varying amounts of water. We claim: E. An explosive cartridge characterized by its high

H J K Ammonium Nitrate Sodium Nitrate 5:1------51.86 49.54 48.99 47.99 47.49 Ammonium Nitrate pass ing a Standard No. 10 Sieve------26.6 25.00 25.00 25.00 25.00 Aluminum Powder--- - 3.14 3.00 3. G() 3.00 3.00 Nitrostarch------2.09 155 I. 55 ii. 55 11. 55 Calcium Carbonate 0.20 0.20 0.20 0.20 0.20 Wood Flour------6.54 6.25 6.25 6.25 6.25 Carbon Black- 0.0i 0.0 G, 0. 0.01 0.01 Water------4.45 5.0 6.0 6.5 100.00 100. GO 100.00 100.00 100.00 Loading Density------... 08-10 | 1.48-1.52 1, 48-1.52 , 48-352 1,48-1.52 Cap Sensitivity.------8 4. 4 |------

it is apparent from I that the addition of 4.45% water 20 greatly increased the sensitivity of the mixture. The seasi sensitivity to detonation containing a granular explosive tivity continued high as the amount of water added in mixtlire consisting essentially of ammonium nitrate as the creased to 5% but then began to decrease, was much less principal explosive component and including from about at 6% and when 6.5% water was used the mixture became 1% to 6% of water and from about 1% to 4% of finely useless, due to caking. divided aluminum, such mixture being in substantially Example 10 5 unset and uncaked form and in which the explosive mix

E F M N

- Ammonium Nitrate-Sodium Nitrate 5:l------53.44 51,04 55.0i 52.54 Ammonium Nitrate passing a Standard No. 10 sieve------26.5 25.00 26.5 25.00 Aluminum Powder--- 1.57 1.50 ------NitroStarch------12.09 1.55 2.09 11. 55 Magnesium. Oxide-- 0.20 0.20 0.20 Wood Four- 6.25 6.54 6.25 Carbon Black- 0.0 0.0 0.01 Water------4.451------4.45 00, 00 100.00 100.00 100.00 Loading Density------1.08-10 | 1.48-1.52 . 08-. 10 1. 48-1.52 Cap Sensitivity------0 8 (1) (1) i Both failed with No. 16 caps, and with 6 g. PETN boosters. M and N are included for comparison with aluminum ture comprises from 7% to 12% of additional explosive containing mixtures. M and N are each of the same order components selected from the group consisting of nitro of sensitivity and each is much less sensitive than either 45 Starch, nitroglycerine, pentolite, cyclonite and trinitro E or F. If the 6 gram pentaerythritol tetranitrate cap were toluene. included in the standard cap scale, it would be equiva 2. A cartridge as specified in claim 1 in which the lent to at least a No. 50 cap. mixture comprises from 5% to 7% of carbonaceous ma terial selected from the group consisting of coal, char Example II 50 coal, carbon black, wood flour and starch. A mixture was prepared in the same way as in Example 3. An explosive cartridge characterized by its high 4E, except that it was packed to a density of 1.385 in sensitivity to detonation containing a granular explosive 14' x 4' cartridges. The standard 1’ x 4' cartridge was mixture consisting essentially of ammonium nitrate as not used because it was too small to allow for the larger 55 the principal explosive component and including from booster required. At this high density, complete detona about 1% to 6% of water and from about 1% to 4% of tion was not obtained even when 6 grams of pentaerythri finely divided aluminum, such mixture being in substan tol tetranitrate was used as a booster. Thus, it is seen that tially unset and uncaked form and in which the explosive the dry mixture even at a density of 1.385 is very much mixture includes from 7 to 12% of an explosive nitrated less sensitive than the moist mixture at densities in the 60 organic sensitizer as an additional explosive component. neighborhood of 1.50. In contrast, a sample prepared as in Example 4F using References Cited loading by gentle bumping to obtain a powder density of UNITED STATES PATENTS 1.10-1.15 was sensitive to a No. 4 cap. 2,063,572 12/1936 Woodbury et al. ------52-5 65 2,836,484 5/1958 Streng et al. ------52-15 Example 12 2,860,041 11/1958 Griffith et al. ------52-14 A mixture was prepared in Example 9 loading the 2,867,172 1/1959 Hradel ------52-14 cartridge by gentle bumping to obtain a powder density 2,463,709 3/1949 McFarland ------52-14 of approximately 1.12. Under these conditions the ma terial was sensitive to a No. 2 cap and detonated almost 70 BENJAMIN R. PADGETT, Primary Examiner. completely with a No. 16 cap. LEON D. ROSDOL OSCAR R. VERTIZ, ROGER L. All proportions of aluminum, water and ammonium CAMPBELL CARL D. QUARFORTH, Examiners. or other are by weight of these three A. D. AKERS, Assistant Examiner.